Fire extinguishing apparatus

ABSTRACT

A fire extinguishing apparatus ( 10 ) producing a mist of water vapour with a median droplet diameter of between 50 and 500 micron for extinguishing fires in a confined risk area. The mist being generated through nozzles ( 18 ) operating at &lt;2000 kPa (i.e. low pressure). The fire extinguishing apparatus using less than 1.0 litres of water per cubic meter of the risk area in which the fire is contained (i.e. a small volume of water).

FIELD OF THE INVENTION

The present invention relates to a fire extinguishing apparatus andmethod relying upon a non-flammable liquid, such as water forextinguishing fire including Class A and B fires with a mist formed froma relatively small amount of liquid at a relatively low pressure. Thefire extinguishing apparatus intended for use in closed areas, such as,for example, in engine rooms, pump rooms, machinery spaces, computerrooms, storage rooms and the like. More particularly, the presentinvention relates to a fire extinguishing apparatus intended for use asa replacement for an existing fire extinguishing apparatus based uponthe use of the now banned HALON.

Hereinafter, the present invention will be described with particularreference to use with liquid being water although it could be used withother non-flammable liquids which absorb heat as they vaporise.

BACKGROUND OF THE INVENTION

In fighting fires it is known that there are three major contributingfactors to the continuation of the fire. These factors are heat, oxygenand fuel and the interrelationship of these factors is shown pictoriallyin FIG. 6. Conventionally when extinguishing fires, fire fighters act toremove at least one of the three elements necessary for combustion.Typically, fire fighters use either water, CO₂, halon, dry chemical orfoam. Water acts by removing the heat from the fuel, whilst carbondioxide works by displacing the oxygen.

Another aspect of combustion is a chain flame reaction indicated by acircle which contains the triangle, as shown in FIG. 6. The chain flamereaction relies upon free radicals which are created in the combustionprocess and are essential for of its continuation. Halon operates byattaching itself to the free radicals and thus preventing furthercombustion by interrupting the flame chain reaction.

The main disadvantage of water is that considerable amounts of water arerequired in extinguishing a fire which leads to considerable damage bythe water. Also, in some instances suitable quantities of water toextinguish the fire are not available. Carbon dioxide and halon bothhave the disadvantage that all people must be evacuated from the area inwhich they are to be used must be evacuated since it will becomeimpossible for the people to breathe. For this reason, fire fightersusing these extinguishing agents must use breathing apparatus. Also, forCO₂ and Halon to extinguish the fire any ventilation of the area must beshut down. Halon has further disadvantage that it is highly toxic andvery damaging to the environment. For those reasons, the use of halon inextinguishing fires has been banned in most circumstances.

The present invention overcomes the above disadvantages by using anon-flammable liquid, such as water, to reduce the heat of the vapouraround the fuel, reduce the heat of the fuel, displace the oxygen, andinterrupt the flame chain reaction. That is, the liquid attacks allparts of the combustion process except for removing the fuel. Theinvention is based upon the generation of a relatively fine mist ofliquid (referred as a mist), such as water, which displaces the oxygen,and upon heating evaporates and expands to further displace the oxygen.Upon expansion the water mist absorbs heat from the vapour around thefuel and from the fuel. Also, the mist interrupts the flame chainreaction by attaching to the free radicals. The mist also has asmothering effect and a cooling effect upon the fire. For these reasons,the mist has the surprising result that a relatively small amount ofwater can safely be used to extinguish both A and B class fires as wellas electrical fires.

The mist generated by the fire extinguishing apparatus of the presentinvention is not a water on flame scenario. Its operation is more akinto gaseous fire extinguishing mediums such as CO₂ or halon.

These surprising results occur due to the very rapid evaporation ratepossible with a fine mist of liquid (typically 50-500 microns), the heatabsorption characteristics of water as it vaporises, the ability of thefine mist to reduce the convection of heat from the fire to surroundingobjects and the ability of the mist to displace oxygen. This is due tothe expansion ratio of water from liquid to vapour.

With the fire extinguishing apparatus of the present invention a typicalfire confined to a room or the like can be entirely extinguished withinabout 30 seconds with a number of nozzles each spraying about 0.4 litresof water as mist at about 20 bar, with one nozzle per 2.65 m³. This is avery small rate of application of water to douse a fire when compared tothe prior art.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide a fireextinguishing apparatus which uses a mist generated from non-flammableliquid applied in relatively small volumes to interrupt the combustionprocess of a fire in a closed space.

In accordance with one aspect of the present invention there is provideda fire extinguishing apparatus for extinguishing a fire located in arisk area, the fire extinguishing apparatus comprising:

a storage reservoir containing a non-flammable liquid;

a spray means for spraying the liquid into the risk area, the spraymeans forming a mist having a droplet size which enhances theapplication of the mist to the fire and hence increase the ability forthe liquid to extinguish the fire;

a propelling means for propelling the liquid out of the storagereservoir and through the spray means under pressure for forming themist;

a sensor means for detecting the presence of a fire in the risk area;

a control means in operative association with the sensor means forcontrolling the propelling means for propelling the liquid out of thestorage reservoir.

In accordance with another aspect of the present invention there isprovided a method for extinguishing a fire, the method comprising thesteps of:

directing a spray means into the risk area;

propelling non-flammable liquid through the spray means under pressurefor forming a mist having a droplet size which creates an atmospherethat will not support combustion.

Typically, the non-flammable liquid is water.

Preferably, the spray means includes a plurality of nozzlesinterconnected by pipes.

Preferably, the mist has a droplet size with a median volume diameter orless than about 500 microns.

Typically, the propelling means is a gas contained in the storagereservoir under elevated pressure. Typically, the gas is dry nitrogen.Typically, the gas is pressurised to about 20 bar in the storagereservoir prior to operation of the fire extinguishing apparatus.

BRIEF INTRODUCTION OF HE DRAWINGS

An exemplary embodiment of the present invention will now be describedwith particular reference to the accompanying drawings, in which:

FIG. 1 is a perspective view, seen from above, of an engine room of aship shown fitted with a fire extinguishing apparatus in accordance withthe present invention;

FIG. 2 is a graph showing the fire extinguishing capabilities of thefire extinguishing apparatus of FIG. 1, in a test facility, forextinguishing ignited isopropanol, petrol and diesel;

FIG. 3 is a graph similar to FIG. 2 but showing a comparison of theextinguishing capabilities of the fire extinguishing apparatus of FIG. 1and the use of carbon dioxide on ignited petrol;

FIG. 4 is a graph showing typical maximum fire temperaturecharacteristics of fires treated with the fire extinguishing apparatusof FIG. 1;

FIG. 5 is a cascade test facility for testing the fire extinguishingapparatus of FIG. 1; and,

FIG. 6 is a pictorial representation of the combustion triangle andflame chain reaction circle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIG. 1 there is shown a fire extinguishing apparatus 10 comprising apressurised container 12, pipes 14 and 16, a plurality of nozzles 18, aplurality of fire detectors 20 and a control panel 22.

Also shown in FIG. 1 is an engine room 100 having a surrounding wall 102within which is located an engine 104, fuel tanks 106, an exhaust pipe108, an exhaust muffler 110, a heat exchanger 112, and a propeller shaftwell 114. The engine room 100 is a typical layout of the engine room ofa ship.

The container 12 is typically made from galvanised metal materials andcapable of withstanding pressures up to for example 3000 kPa. Typically,the container 12 has a charge of distilled water maintained underpressure by a charge of dry nitrogen. Typically, the container 12 has acapacity between about 5 and 30 litres. However, the container 12 couldhave virtually any capacity, although by the nature of the operation ofthe present invention the container 12 may be much smaller than priorart containers.

Typically, the pressurised container 12 is located proximate thesurrounding wall 102. The container 12 has a control valve 30 attachedto its outlet for controlling the expulsion of the water under pressurefrom the container 12. The control valve 30 may be actuated electricallyor mechanically and the actuation may be automatic or manual.

The pipes 14 and 16 form a plumbing network 36 attached to the flow ratecontrol valve 32 and each carry a plurality of the nozzles 18. The pipes14 and 16 and hence the nozzles 18 are strategically located about theengine room 100, as described hereinafter. Also, the nozzles 18 areoriented in strategic directions from the pipes 14 and 16. For example,the nozzles 18 are oriented so as to ensure that the pressurised waterfrom the container 12 can be sprayed to all areas of the engine room 100and to concentrate on areas of higher flame potential. Preferably, thepipes 14 and 16 are oriented about a roof of the engine room 100 andinto the propeller shaft well 114. The nozzles 18 are then orienteddownwardly and/or outwardly from the pipes 14 and 16. Typically, theplumbing network 36 is coupled to the pressurised container 12 by aflexible water way. Typically, the plumbing network 36 has a borediameter not less than 12 mm. Also, the plumbing network 36 preferablyis capable of withstanding internal pressures of at least 3000 kpa.Further, it is preferred that the plumbing network be of a looped designand that there be no ends in the lines of the plumbing network.

The nozzles 18 are typically formed from brass or stainless steel andinclude a swirl chamber and an elongate cone inlet filter. The swirlchamber increases the atomisation of water passing through it and thefilter inhibits blockage 6f the swirl chamber by detritus material. Thenozzles 18 typically produce a droplet size between 50 and 500 microns,more particularly between 250 and 400 microns. The spray pattern fromthe nozzles 18 is typically about 80° at a pressure of 2000 kpa (20bar). Also, the nozzles 18 typically have a minimum orifice size ofabout 1 mm². The nozzles 18 use the liquid pressure alone to producevery finely atomised droplets in a hollow cone spray pattern withuniform distribution for achieving high misting performance. The nozzles18 used in the exemplary embodiment are typically those available underthe Registered Trade Mark UNIJET. The following specific nozzles areconsidered particularly useful:

TYPE FLOW RATE (L/MIN) PRESSURE (BAR) TN-4 0.65 20 TN-6 0.83 20 TN-80.96 20 TN-10 1.06 20

The nature and size of the nozzles 18 to be used in a particular engineroom 100 (or other risk area) depends upon a number of factors and canbe calculated as shown in example 1.

EXAMPLE 1

To determine the quantity and type of nozzles 18 to use the followingcalculations can be performed.

The calculation is performed according to the following glossary ofterms:

G.V.—the gross volume which represents the volume of the risk area(height H×width W×length L);

N.V.—the nett volume which represents the gross volume of the risk areaminus all solid objects within it;

W.R.—water required which represents the amount of water required inlitres to be introduced into the risk area;

N.N—the number of nozzles required to spray the mist into the risk areain a substantially uniform manner;

90FR—a ninety second flow rate which represents the volume of waterwhich flows through each nozzle 18 in 90 seconds at 20 bar (typically1.26 litres);

C.F.—a compensating factor which we have developed throughexperimentation for each flow rate of nozzle 18 as shown below:

2.8 for TN-4 type nozzle 18

2.1 for TN-6 type nozzle 18

1.8 for TN-8 type nozzle 18

1.1 for TN-10 type nozzle 18

W.V.—water volume in cubic metres (i.e. W.R./1000)

P.V.—potential vapour which represents the expansion ratio ofvaporisation of water, namely 1700 * W.V.;

P.F.B.—potential fuel by-products due to combustion and represents theamount of CO₂ and H₂O which are released as gases during combustion ofthe fuel, for example 212 grams of C₁₅H₃₂ (diesel) produces about 1525litres of CO₂ and H₂O under complete combustion, and about 1284 litresof CO₂ and H₂O for a similar mass of C₈H₁₀ (xylene petrol);

The water capacity and the number of nozzles 18 required is thenrepresented by the following formula:

W.R.=N.V./C.F.

N.N.=W.R./90FR

Thus given a risk area 7 m×4 m×1.7 m, with 3 obstructions one of whichis 1 m×1 m×1 m and the other two obstruction being 1.8 m×0.9 m×0.8 m,and using nozzles 18 of the type TN-6 the number of nozzles 18 requiredis determined as follows:

G.V. = 7 × 4 × 1.7 = 47.6 m³ N.V. = G.V. − (1 × 1 × 1 + 2 × (1.8 × 0.9 ×0.8)) = 47.6 − 3.492 = 44.008 m₃ W.R. = 44.008/2.1 = 20.9 l N.N. =20.9/1.26 = 16.58 nozzles

N.N.=17 NOZZLES

NB: Always round up to the nearest whole number i.e. in this case N.N.is 17 an the volume of water required W.R. must be adjusted accordingly(i.e. W.R. in this example is 21.4 litres).

The fire detectors 20 include a fixed temperature fire detector 40 and arate of rise fire detector 42. The fixed temperature 40 typicallyincludes a bimetallic strip with an extension rod which elevates adiaphragm to make a contact when the ambient temperature increases abovea predetermined temperature. Typically, the fixed temperature is between60 and 100° C. The rate of rise fire detector 42 typically includes adiaphragm and an air chamber, wherein the chamber leaks air through afence tube in the diaphragm at relatively low rates of rise intemperature but which causes raising of the diaphragm to make a contactat relatively high rates of rise of the fire temperature. Typically, therate of rise fire detector 42 is set to be active when the rate of risein temperature is greater than about 9° C. per minute.

The detectors 20 also typically include smoke detectors. The smokedetectors are preferably located so as to detect air flowing out of therisk area to sense any smoke entrained in the air.

The control panel 22 is located so as to be easily accessed during afire. For example, the control panel 22 may be located on the outside ofthe surrounding wall 102 of the engine room 100. The control panel 22includes a wiring fault detection monitoring system and an activationsystem. The fault detection monitoring system monitors the wiring to thefire detectors 20 and the control valves 30 and 32 for open circuits,short circuits and unstable wiring conditions. The control panel 22 alsosenses the pressure in the pressurised container 22 and issues an alarmin the event that the pressure falls below a predetermined pressure. Theactivation system is of the “detonator” type which causes the controlvalves 30 and 32 to release the pressurised water from the container 12.Typically, the control panel 22 includes a mist release push buttonhaving a lift cover placed over it. The mist release push button isrequired to be activated to manually release the water from thecontainer 12. The control panel 22 is also connected to visual andaudible alarms located in the engine room 100.

In use, the fire extinguishing apparatus 10 is installed into a riskarea, such as the engine room 100, by first calculating the number ofnozzles required, the type of nozzles to use and the volume of waterrequired for example as shown in Example 1. The nozzles 18 are thenspaced about the engine room 100 along the pipes 14 and 16 to thepressurised container 12 via the control valves 30 and 32. The controlpanel 22 is located on the outside of the engine room 100 and wired intothe fire detectors 20 and the control valves 30 and 32 and the audibleand visual alarms.

In the event of a fire or rapid increase in temperature in the engineroom 100 the fire detector 40 or 42 is triggered to initiate the controlpanel 22 to operate the control valves 30 and 32 to release water underpressure out of the container 12. The pressurised water passes along thepipes 14 and 16 to the nozzles 18. The water passes through the filterand swirl chamber of the nozzles 18 and forms a fine mist having amedian droplet diameter between 250 and 500 microns. The median dropletdiameter is an expression of the droplet size in terms of the volume ofthe liquid and is a value where 50% of the total volume of the liquidsprayed is made up of droplets with diameters larger than the medianvalve and 50% smaller than the median value.

The following test procedures were performed in a test rig situated in aforty foot cargo container having its access doors open at one end andwith a plurality of the nozzles 18 located mid way up the side walls ofthe container. Flammable fuel was placed in a tray located on the floorof the container intermediate of the length of the container. Theresults of the tests are as follows:

TEST 1 Purpose: VISUAL DEMONSTRATION—ISOPROPANOL

EXTINGUISHING MEDIUM WATER MIST FUEL ISOPROPANOL AMOUNT OF FUEL USED 3 lSURFACE AREA OF FIRE 0.636 m² DETECTION TIME 5 s NOZZLE SIZE HF-16ORIFICE SIZE 1.1 mm CAPACITY EACH NOZZLE AT 20 BAR 0.683 l/min CAPACITYALL NOZZLES AT 20 bar 16.4 l/min WATER PRESSURE 2000 kpa (20 bar) SPRAYANGLE 84° NUMBER OF NOZZLES 24 NUMBER OF EFFECTIVE NOZZLES 14 TO 16MEDIAN DROPLET SIZE 375-400 MICRONS TIME TO EXTINGUISH 23 s RATE OFABSORPTION 21.7° C./s

The number of nozzles 18 which were effective was less than the totalnumber of nozzles 18 since the doors of the container where open.

TEST 2 Purpose: VISUAL DEMONSTRATION—PETROL

EXTINGUISHING MEDIUM WATER MIST FUEL PETROL AMOUNT OF FUEL USED 3 lSURFACE AREA OF FIRE 0.636 m² DETECTION TIME 3 s NOZZLE SIZE HF-16 × 16HF-32 × 8 ORIFICE SIZE HF-16 = 1.1 mm HF-32 = 1.5 mm CAPACITY EACHNOZZLE AT 20 bar 21.8 l/min WATER PRESSURE 2000 kpa (20 bar) SPRAY ANGLEHF-16 = 84° HF-32 = 91° NUMBER OF NOZZLES 24 NUMBER OF EFFECTIVE NOZZLES16 MEDIAN DROPLET SIZE HF-16 = 375-400 micron HF-32 = 350-375 micronTIME TO EXTINGUISH 13 s RATE OF ABSORPTION 1.123° C./s

TEST 3 Purpose: VISUAL DEMONSTRATION—DIESEL

EXTINGUISHING MEDIUM WATER MIST FUEL DIESEL AMOUNT OF FUEL USED 3 lSURFACE AREA OF FIRE 0.363 m² DETECTION TIME 12 s NOZZLE SIZE HF-16ORIFICE SIZE 1.1 mm CAPACITY EACH NOZZLE AT 20 bar 0.683 l/min CAPACITYALL NOZZLES AT 20 bar 16.4 l/min WATER PRESSURE 2000 kpa (20 bar) SPRAYANGLE 84° NUMBER OF NOZZLES 24 NUMBER OF EFFECTIVE NOZZLES 24 MEDIANDROPLET SIZE 375-400 MICRONS TIME TO EXTINGUISH 6 s RATE OF ABSORPTION0.33° C./s

TEST 4 Purpose: COMPARISON OF MIST WITH CO₂

EXTINGUISHING MEDIUM WATER MIST FUEL PETROL AMOUNT OF FUEL USED 2 lSURFACE AREA OF FIRE 0.636 m² DETECTION TIME 5 s NOZZLE SIZE HF-16ORIFICE SIZE 1.1 mm CAPACITY EACH NOZZLE AT 20 bar 0.683 l/min CAPACITYALL NOZZLES AT 20 bar 16.4 l/min SPRAY ANGLE 84° NUMBER OF NOZZLES 24NUMBER OF EFFECTIVE NOZZLES 24 MEDIAN DROPLET SIZE 375-400 MICRONS TIMETO EXTINGUISH 12 s

This is hereinafter referred to as the “mist test”.

TEST 5 Purpose: COMPARISON OF MIST WITH CO₂

EXTINGUISHING MEDIUM CARBON DIOXIDE FUEL PETROL AMOUNT OF FUEL USED 2 lSURFACE AREA OF FIRE 0.636 m² DETECTION TIME 5 s QUANTITY OF CO₂ 32 kgNUMBER OF NOZZLES 6 NUMBER OF EFFECTIVE NOZZLES 6 TIME TO EXTINGUISH 17s

This is hereinafter referred to as the “CO₂ test”.

In the test procedures each of the fuels was ignited and allowed toflame up for between 25 to 60 seconds, after which time the fireextinguishing apparatus 10 was activated to extinguish the fire. Thetemperature inside the container was monitored from the time of ignitionof the fuel until after extinguishing of the fire produced thereby.These results are shown graphically in FIGS. 2 and 3. FIG. 2 relates totests 1 to 3, and tests 4 and 5 are shown graphically in FIG. 3. Anarrow indicated “I” represents the point in time at which the fuel wasignited and an arrow indicated “E” indicates the point in time at whichthe fire was extinguished.

The result of each of the tests of the fire extinguishing apparatus 10is that the fire was extinguished in a relatively short period of timeand typically less than the 25 seconds. It should also be noted,particularly as shown in FIG. 3, that the temperature reducing effect ofthe fire extinguishing apparatus 10 is greater than that of carbondioxide. This occurs because as the temperature in the risk areaincreases the volume of the water mist increases dramatically as itchanges state from water mist to water vapour. Water vapour has a volumewhich is 1700 times greater than the volume of the water from which itwas produced. Hence, the water vapour further displaces the oxygen fromthe risk area and inhibits the risk area from maintaining combustion.Also, in the change of state of the water from liquid to gas it absorbsheat 540 times greater than that of the liquid phase. Further, theincrease in temperature of the risk area decreases the specific gravityof the water which increases its velocity, decreases its droplet sizeand increases the flow of the water throughout the risk area. That is,the water mist is more effective with increase in temperature of therisk area. This does not usually occur with other fire fighting mediums.

In FIG. 4 there is shown a graph of temperature versus time showing theminimum operational characteristics of the fire extinguishing apparatus10. The graph shows a pre-burn period denoted P, a stabilisingtemperature period denoted ST (which is typically 90 seconds) and at theend of which the fire extinguishing apparatus 10 is activated.Thereafter, the fire is extinguished within an extinguishing perioddenoted E which is typically less than 60 seconds and the container 12is fully discharged within a discharge period denoted D which istypically greater than 90 seconds. During the pre-burn period the riskarea typically reaches a temperature in excess of 300° C., whichtemperature is maintained during the temperature stabilisation periodST. Typically, the temperature in the risk area is reduced to 60% of thetemperature in the stabilised temperature period ST before the container12 is fully discharged. Typically,the final temperature within the riskzone is less than 250° C. The tests shown in FIGS. 2 and 3 show thatthese results are achievable with the fire extinguishing apparatus 10 ofthe present invention.

The abovementioned test were conducted using a cascade apparatus 200shown in FIG. 5. Th cascade tray 204 is designed to simulate fuelleaking onto a hot manifold. The cascade apparatus 200 comprises arelatively large box tray 202 having an area of approximately 1 squaremetre, a flat cascade tray 204 having a surface area of approximately0.5 square metres, upon which is located a relatively small box tray206. The small box tray 206 has a plurality of holes 208 for allowingdiesel from the box tray 206 to fall onto the flat cascade tray 204. Thecascade tray 204 has legs 210 spacing it above the tray 202, and thetray 206 has legs 212 spacing it above the cascade tray 204. Typically,the tray 202 has petrol and/or isopropanol located in it. In use, thecascade tray 204 becomes extremely hot and causes ignited fuel from thetray 206 to explode and be projected off the cascade apparatus 200.

A further test of the fire extinguishing apparatus 10 of the presentinvention was conducted in a risk area having a volume of 500 m³ (10m×10 m×5 m) with 190 of the same nozzles 18 as used in the previoustest. In this test 90 litres of fuel was used having an area of 7 m².The fuel was contained in the cascade tray 204 and 6 other traysincluding pool fires and a diesel oil pressure fire (representing a firefrom a ruptured fuel line). All of the trays were ignited and allowed toburn for two minutes before activation of the fire extinguishingapparatus 10 of the present invention.

During the test it was observed that the colour of he combustionby-products changed from thick black to white immediately the fireextinguishing apparatus 10 was started. The results of the test was thatall of the fires were extinguished within 30 seconds and observerswalked into the risk area before the completion of the 90 second periodover which the mist is released into the risk area. The observersexperienced no difficulty in breathing during that time. It appears fromthis test that the fire extinguishing apparatus 10 lead to suppressionof smoke and causes combustion by-products to fall out of the air.

The fire extinguishing apparatus 10 of the present invention has theadvantage that it can use water mist to fill a risk area so as tointerrupt the flame chain reaction in the combustion cycle so as toprevent combustion within the risk area. Also, the water vapour has theeffect of greatly reducing the heat within the risk area and displacingoxygen within the risk area due to the change in the state of the waterfrom a liquid to a vapour (mist). Hence, the fire extinguishingapparatus 10 of the present invention has the surprising result that itcan use a relatively small quantity of water to extinguish a flamecaused by a relatively large quantity of highly flammable liquid. InTable 1 there is shown a comparison of the benefits of the fireextinguishing apparatus 10 of the present invention (referred to asMISTEX) with conventional fire extinguishing systems.

TABLE 1 COMPARISONS SPRINKLER HALON CO₂ MISTEX NON-TOXIC YES NO NO YESEXTINGUISH NO YES YES YES A & B CLASS FIRES ENVIRONMENTALLY YES NO NOYES FRIENDLY REQUIRED YES NO NO NO FIRE PUMP LIGHT WEIGHT NO YES NO YESSERVICE NO NO NO YES ACCESSIBLE BY CREW HIGH HEAT YES NO NO YESABSORPTION COST NO YES NO YES EFFECTIVENESS RUNNING TIME (IN-BUILTSAFETY) N/A NO NO YES NO EVACUATION YES NO NO YES PLAN REQUIRED SERVICEAND REFILL N/A NO NO YES COST EFFECTIVENESS EFFECTIVE IN SEMI- YES NO NOYES VENTILATED AREAS

Modifications and variations such as would be apparent to a skilledaddressee are considered within the scope of the present invention. Forexample, a heat absorber and fuel emulsifier such as, for example, aliquid under the trade mark PHIREX could be added to the water toincrease its fire extinguishing capabilities. Also, any form of firedetector could be used in the fire extinguishing apparatus, such as, forexample, radioisotope based fire detectors, ionic chamber detectors,beam detectors, ultraviolet detectors or the like.

What is claimed is:
 1. A fire extinguishing apparatus for extinguishinga fire located in a risk area, the fire extinguishing apparatuscomprising: spray means for spraying non-flammable liquid therefrom intothe risk area, delivery means for passage of the non-flammable liquidfor delivery thereof under pressure to said spray means, detector meansfor detecting the presence of a fire in the risk area, and fluiddelivery control means to allow delivery of the non-flammable liquid viasaid delivery means to said spray means following actuation of saidfluid delivery control means, wherein, in use, said spray means spraysthe non-flammable liquid therefrom to form a mist having a mediandroplet size of substantially 500 microns or less, said non-flammableliquid is sprayed from said spray means at a rate of substantially 1liter or less per minute per cubic meter of volume of the risk area, andsaid non-flammable liquid is sprayed from said spray means into saidrisk area to form said mist the non-flammable liquid, such that saidmist of non-flammable liquid droplets can be applied to the fire toextinguish the fire.
 2. A fire extinguishing apparatus according toclaim 1, wherein the median droplet size is between 250 and 400 micron.3. A fire extinguishing apparatus according to claim 1, wherein thespray means comprises a plurality of nozzles, the number of nozzlesrequired for the risk area being determined as a function of the airvolume of the risk area, the flow rate of the nozzles and a compensatingfactor, the function being: N.N.=[A.V./C.F.]/90FR where N.N. is thenumber is nozzles, A.V. is the air volume of the risk area, C.F. is thecompensating factor, and 90FR is a volume of water which flows throughone of the nozzles in 90 seconds.
 4. A fire extinguishing apparatusaccording to claim 3, wherein the nozzles each have a discharge rate of<2 liters/minute.
 5. A fire extinguishing apparatus according to claim3, wherein the nozzles each have a spray angle of >70°.
 6. A fireextinguishing apparatus according to claim 3, wherein the nozzles eachhave a hollow spray pattern.
 7. A fire extinguishing apparatus accordingto claim 3, wherein, in use, the nozzles are spaced about 1 meter apartin the risk area.
 8. A fire extinguishing apparatus according to claim1, wherein the detector means comprises a temperature detector set tobecome active at between 60-100° C.
 9. A fire extinguishing apparatusaccording to claim 1, wherein the detector means comprises a rate oftemperature rise detector set to detect rates of temperature rise ofgreater than about 9° C./min.
 10. A fire extinguishing apparatusaccording to claim 1, wherein the detector means comprises a smokedetector.
 11. A fire extinguishing apparatus according to claim 1,wherein the mist is breathable.
 12. A fire extinguishing apparatusaccording to claim 1, wherein propelling means is provided forpropelling the non-flammable liquid via said delivery means to saidspray means and said propelling means comprises dry nitrogen storedunder pressure in a storage reservoir.
 13. A fire extinguishingapparatus according to claim 1, wherein the non-flammable liquid iswater.
 14. A fire extinguishing apparatus according to claim 1, whereinsaid non-flammable liquid is sprayed from said spray means at a rate inthe range from 0.1 liter per minute per cubic meter of volume of therisk area to 0.63 liter per minute per cubic meter of volume of the riskarea.
 15. A fire extinguishing apparatus according to claim 1, whereinsaid non-flammable liquid is sprayed from said spray means at a rate inthe range from 0.25 liter per minute per cubic meter of volume of therisk area to 0.44 liter per minute per cubic meter of volume of the riskarea.
 16. A fire extinguishing apparatus according to claim 1, whereinthe median droplet size is between substantially 50 and 500 microns. 17.A fire extinguishing apparatus according to claim 1, wherein, in use,said spray means operates for substantially 90 seconds or less toextinguish the fire.
 18. A fire extinguishing apparatus according toclaim 1, wherein, in use, the non-flammable liquid is delivered from astorage reservoir means via said delivery means to said spray means. 19.A fire extinguishing apparatus according to claim 18, wherein saidstorage reservoir means comprises a container.
 20. A fire extinguishingapparatus according to claim 1, wherein propelling means is provided forpropelling the non-flammable liquid via said delivery means to saidspray means.
 21. A fire extinguishing apparatus according to claim 20,wherein, in use, said propelling means propels the non-flammable liquidat a pressure of substantially 2000 kPa or less.
 22. A fireextinguishing apparatus according to claim 20, wherein the propellingmeans comprises a pressurized gas.
 23. A fire extinguishing apparatusaccording to claim 1, wherein control means is provided and enablesactuation of said fluid delivery control means from a location remotefrom said fluid delivery control means.
 24. A fire extinguishingapparatus according to claim 23, wherein said control means is providedin operative association with said detector means for controllingdelivery of said non-flammable liquid to said spray means.
 25. A fireextinguishing apparatus according to claim 24, wherein upon saiddetector means detecting the presence of a fire in the risk area, saiddetector means initiates said control means to actuate said fluiddelivery control means.
 26. A fire extinguishing apparatus according toclaim 1, wherein said fluid delivery control means comprises at leastone valve.
 27. A fire extinguishing apparatus according to claim 1,wherein the non-flammable liquid is an aqueous solution.
 28. A fireextinguishing apparatus according to claim 1, wherein the non-flammableliquid contains additives.
 29. A fire extinguishing apparatus accordingto claim 3, wherein each said nozzle comprises a swirl chamber toincrease atomization of the non-flammable liquid that passestherethrough.
 30. A fire extinguishing apparatus according to claim 3,wherein, in use, said nozzles are arranged such that non-flammableliquid is sprayed to all areas of the risk area.
 31. A method ofextinguishing a fire in a risk area comprising the steps of: detectingthe presence of a fire in the risk area, actuating fluid deliverycontrol means for delivery of a non-flammable liquid, delivering thenon-flammable liquid under pressure to spray means, and directing aspray of the non-flammable liquid from the spray means into the riskarea, characterized by spraying the non-flammable liquid into the riskarea to form a mist having a median droplet size of substantially 500microns or less, spraying the non-flammable liquid at a rate ofsubstantially 1 liter or less per minute per cubic meter of volume ofthe risk area, and spraying the non-flammable liquid into the risk areato form said mist of the non-flammable liquid, such that said mist ofnon-flammable liquid droplets is applied to the fire to extinguish thefire.
 32. A method of extinguishing a fire according to claim 31,wherein the non-flammable liquid is sprayed from the spray means at arate in the range from 0.25 liter per minute per cubic meter of volumeof the risk area to 0.44 liter per minute per cubic meter of volume ofthe risk area.
 33. A method of extinguishing a fire according to claim31, wherein the non-flammable liquid is sprayed from the spray means ata rate in the range from 0.25 liter per minute per cubic meter of volumeof the risk area to 0.44 liter per minute per cubic meter of volume ofthe risk area.
 34. A method of extinguishing a fire according to claim31, wherein the non-flammable liquid is sprayed from the spray meansinto the risk area to form a mist having a median droplet size betweensubstantially 50 and 500 microns.
 35. A method of extinguishing a fireaccording to claim 31, wherein the non-flammable liquid is sprayed fromthe spray means into the risk area to form a mist having a mediandroplet size between substantially 250 and 400 microns.
 36. A method ofextinguishing a fire according to claim 31, further comprising operatingthe spray means for substantially 90 seconds or less to extinguish thefire.
 37. A method of extinguishing a fire according to claim 31,further comprising delivering the non-flammable liquid from a storagereservoir means via delivery means to said spray means.
 38. A method ofextinguishing a fire according to claim 31, further comprisingpropelling the non-flammable liquid under pressure to the spray means.39. A method of extinguishing a fire according to claim 31, wherein thenon-flammable liquid is propelled at a pressure of substantially 2000kPa or less.
 40. A method of extinguishing a fire according to claim 31,further comprising actuating said fluid delivery control means from alocation remote from said fluid delivery control means.
 41. A method ofextinguishing a fire according to claim 31, further comprisinginitiating control means to actuate said fluid delivery control meansupon detecting the presence of a fire in the risk area by detectormeans.
 42. A method of extinguishing a fire according to claim 31,wherein the spray means comprises a plurality of nozzles, anddetermining the number of nozzles required for the risk area as afunction of the air volume of the risk area, the flow rate of thenozzles and a compensating factor, the function being:N.N=[A.V./C.F.]/90FR where N.N. is the number of nozzles, A.V. is theair volume of the risk area, C.F. is the compensating factor ashereinbefore defined, and 90FR is the volume of water which flowsthrough one of the nozzles in 90 seconds.
 43. A method of extinguishinga fire according to claim 42, wherein the non-flammable liquid issprayed from the nozzles at a discharge rate of less than substantially2 litres/minute.
 44. A method of extinguishing a fire according to claim42, wherein the non-flammable liquid is sprayed from each nozzle at aspray angle of greater than substantially 70°.
 45. A method ofextinguishing a fire according to claim 42, wherein the non-flammableliquid is sprayed from each nozzle with a hollow spray pattern.
 46. Amethod of extinguishing a fire according to claim 42, wherein thenozzles are spaced about 1 meter apart in the risk area.
 47. A method ofextinguishing a fire according to claim 42, further comprising arrangingthe nozzles such that the non-flammable liquid is sprayed to all areasof the risk area.
 48. A method of extinguishing a fire according toclaim 31, further comprising detecting the presence of a fire bydetecting an increase in temperature above a predetermined temperature.49. A method of extinguishing a fire according to claim 48, wherein saidpredetermined temperature is in the range of substantially 60° to 100°C.
 50. A method of extinguishing a fire according to claim 31, furthercomprising detecting the presence of a fire by detecting rates oftemperature rise of greater than about 9° C./min.
 51. A method ofextinguishing a fire according to claim 31, further comprising detectingthe presence of a fire by detecting smoke in the risk area.
 52. A methodof extinguishing a fire according to claim 31, wherein the non-flammableliquid is water.
 53. A method of extinguishing a fire according to claim31, wherein the non-flammable liquid is an aqueous solution.
 54. Amethod of extinguishing a fire according to claim 31, wherein thenon-flammable liquid contains additives.